TWI663765B - Metal terminal-coated resin film for secondary battery, manufacturing method thereof, and battery pack - Google Patents

Abstract

An object of the present invention is to provide a metal terminal-coated resin film for a secondary battery, which can ensure the filling property, adhesiveness, and insulation of the end portion of the lead among the tabs used in a laminated packaging material for a secondary battery. 2. The shape of the sealant is excellent and the overall performance is excellent; and a method for manufacturing the metal terminal-coated resin film for the secondary battery and a battery pack using the metal terminal-coated resin film for the secondary battery are provided. The metal terminal-coated resin film (24) for a secondary battery of the present invention is a resin film for a metal terminal of a secondary battery that is laminated on the metal terminal (26) connected to the positive or negative electrode of the secondary battery to constitute the resin film. The melt flow rate of at least one layer of the resin in (24) is in a range of 0.1 g / 10 minutes or more and 2.5 g / 10 minutes or less.

Description

Metal terminal-coated resin film for secondary battery, manufacturing method thereof, and battery pack

The present invention relates to a metal terminal-coated resin film for a secondary battery, which has excellent shape stability and adhesion when heated and can ensure insulation, and a method for manufacturing the metal terminal-coated resin film for a secondary battery. And a battery pack using the metal terminal for a secondary battery covered with a resin film.

Conventional nickel-metal hydride and lead-acid batteries, such as water-based batteries, have limited the voltage of the battery cells to about 1.2V due to the limitation caused by the electrolytic voltage of water. However, nowadays, because it is necessary to miniaturize mobile devices and effectively utilize natural power generation energy, there is a greater need for lithium-ion batteries that can obtain higher voltages and have high energy density. Although metal cans have been used as packaging materials for such lithium-ion batteries in the past, due to the requirements for thinning and diversification of products, "materials that allow resin films to be laminated on low-cost aluminum foils have been gradually used. "Bag-like" laminated packaging material.

A laminated packaging material (hereinafter referred to as a packaging material) 10 for a secondary battery is a laminate composed of a metal foil and a resin. As shown in FIG. 1, the packaging material 10 is generally formed in order from the inner layer: the inner resin layer 11, the inner-layer-side adhesive layer 12, the anti-corrosion treatment layer 13, The barrier layer 14, the anti-corrosion treatment layer 13, the outer layer side adhesive layer 15, and the outer layer 16. The barrier layer 14 is made of aluminum or stainless steel, and the outer layer 16 is made of a single layer film or a multilayer film made of nylon or PET (Poly Ethylene Terephtalate).

In order to remove lithium ions from such a packaging material 10 The battery supplies power and requires electrode terminals called tabs. 3 (a) and (b) are cross-sectional views schematically showing the configuration of the tab 20. This tab 20 is composed of a metal terminal (hereinafter also referred to as a “lead”) 27 and a metal terminal-coated resin film (hereinafter also referred to as “seal”) 24.

The guide plate 27 of the positive electrode uses aluminum, and the surface is mostly anticorrosive Etching surface treatment. When the anti-corrosive surface treatment is performed, a corrosion-resistant protective layer 25 is formed on the surface of the guide piece 27. On the other hand, the negative electrode guide 27 is made of nickel or copper.

The sealant 24 generally uses a single-layer or multi-layer resin film. An example of the sealant 24 of three layers is shown in FIG. Since the sealant 24 is a member disposed between the guide 27 and the packaging material 10, the following three properties are mainly required.

First, it must have both the guide 27 and the inner resin (formed Adhesion of both resins of the inner resin layer 11. Regarding the adhesiveness with the guide sheet 27, the polyolefin resin used for the sealant 24, that is, polypropylene or polyethylene is acid-modified, and a polar group is introduced to improve the adhesiveness.

In addition, as shown by X in FIG. 3 (b), when the sealant 24 is welded to the guide 27, the end portion 27a of the guide 27 must be filled with the molten sealant resin. In the case of insufficient filling, the guide piece 27 and the sealant 24 cannot be closely adhered, and leakage or peeling may occur when the battery is manufactured. shape. In order to improve the filling property of the sealant 24 to the end portion 27a of the guide, the melt flow rate (MFR) of the sealant resin is increased, and it is important to make the sealant resin flow easily during welding. Among the above-mentioned inner layer resins, polyolefin resins such as polypropylene and polyethylene are generally used. Therefore, by using polyolefin resins also in the above-mentioned sealant resin, good adhesion can be obtained.

Second, ensure insulation. Guide 27 because the current The battery-derived terminals must be insulated from other components. The most insulative part of the tab member is the corner portion 27 b of the guide piece 27 as shown in Y in FIG. 3 (b). The corner portion 27b of the guide piece may pierce the sealant 24 when the guide piece 27 has a burr or the like; when the guide piece 27 and the sealant 24 are welded, the pressure and temperature conditions are too high, the seal is sealed. The film thickness of the glue 24 may become too thin. Therefore, the film thickness of the sealant resin in this portion (ie, the corner portion 27b of the guide piece) is most likely to be thinned, and the insulation property is liable to be reduced. In order to solve the above problems, a resin having a low melt flow rate must be used, making it difficult for the resin to flow during welding.

Third, the shape of the sealant 24 is maintainable. As shown in Figure 3 (b) As shown by Z, the tab 20 has a portion made of only a sealing resin. This part may swell or flex due to heating and cooling conditions during welding, and may sag (harden in a deformed state) due to its own weight after welding.

In order to obtain the above characteristics, it is proposed in Patent Documents 1 and 2 The solution is to use a laminated structure with different melt flow rates to form a three-layer structure. During welding, a high-flow layer that is easy to flow with the resin and a low-flow layer that is difficult to flow with the resin are laminated to combine the resin with the end of the guide. The covering property of 27a and the insulating property obtained by maintaining the film thickness of the corner portion 27b of the guide. However, in the applications of typical large-capacity batteries such as automotive batteries and accumulators, the thickness of the guide piece 27 tends to increase, and the filling property of the sealant 24 is more severe. In addition, because of the large battery capacity of these large batteries, the requirements for insulation are becoming more and more severe. If the structures of Patent Documents 1 and 2 have insufficient performance.

Prior art literature Patent literature

Patent Document 1 Japanese Patent No. 4498639

Patent Document 2 Japanese Patent No. 4930054

Therefore, the present invention has been made in view of the foregoing circumstances, and an object thereof is to provide a metal terminal-coated resin film for a secondary battery, which can ensure the filling property, adhesiveness, insulation, and shape of the sealant at the end portion of the guide. The present invention provides a method for manufacturing a metal terminal-coated resin film for a secondary battery and a battery pack using the metal terminal-coated resin film for a secondary battery.

In order to solve the above-mentioned problem, one aspect of the present invention is a resin film coated with a metal terminal for a secondary battery, which is a laminated metal terminal for a secondary battery that covers a metal terminal connected to the positive or negative electrode of the secondary battery. The coated resin film is characterized in that the melt flow rate of at least one layer of the resin constituting the resin film is within a range of 0.1 g / 10 minutes or more and 2.5 g / 10 minutes or less.

As long as the above-mentioned metal battery for a secondary battery is coated with a resin film, it has at least one film layer having a melt flow rate in a range of 0.1 g / 10 minutes or more and 2.5 g / 10 minutes or less. Therefore, it is difficult for the resin to flow during welding, so that Maintain insulation.

In addition, another aspect of the present invention is a secondary battery. A resin film coated with a metal terminal is a resin film coated with a metal terminal for a laminated secondary battery that covers a metal terminal connected to a positive electrode or a negative electrode of a secondary battery, and the resin film is composed of three layers, and In the case where the intermediate layer of the resin film is a core layer and the other layers are surface layers, the difference between the melt flow rate of the core layer and the surface layer is within a range of 5 g / 10 minutes or more and 30 g / 10 minutes or less.

As long as it is the resin film coated with the metal terminal for the secondary battery described above, the difference between the melt flow rate of the core layer and the surface layer is within a range of 5 g / 10 minutes or more and 30 g / 10 minutes or less. It can ensure the insulation of the core layer and the coating of the resin on the surface layer.

In addition, another aspect of the present invention is a secondary battery. A resin film coated with a metal terminal is a resin film coated with a metal terminal for a laminated secondary battery that covers a metal terminal connected to a positive electrode or a negative electrode of a secondary battery, and the resin film is composed of three layers, and In the case where the intermediate layer of the resin film is a core layer and the other layers are surface layers, the film thickness of the core layer is in a range of 20 μm to 200 μm.

As long as the above-mentioned metal battery for a secondary battery is coated with a resin film, the thickness of the core layer is 20 μm or more, so that insulation can be ensured even when heat-sealed or the like is applied during welding. In addition, since the thickness of the core layer is 200 μm or less, it is easy to control the film thickness, and the amount of resin has not increased, which can prevent the cost from being too high.

The above-mentioned metal terminal-coated resin for a secondary battery In the film, at least one of the surface layers of the resin film may also be used as an acid-modified polyolefin resin.

As long as the above-mentioned metal battery for a secondary battery is coated with a resin film, an acid-modified polyolefin layer is provided on at least one of the surface layers, so that the adhesion to the metal terminal and other resins can be improved.

The above-mentioned metal terminal-coated resin for a secondary battery In the film, the melt flow rate of the resin constituting at least one layer of the resin film may be in a range of 0.1 g / 10 minutes or more and 2.5 g / 10 minutes or less.

As long as the above-mentioned metal film for a secondary battery is coated with a resin film, it has at least one film layer having a melt flow rate in a range of 0.1 g / 10 minutes or more and 2.5 g / 10 minutes or less. Therefore, the resin is difficult to flow during welding, and may Maintain insulation.

The above-mentioned metal terminal-coated resin for a secondary battery In the film, the difference between the melt flow rate of the core layer and the surface layer may be set in a range of 5 g / 10 minutes or more and 30 g / 10 minutes or less.

As long as the metal terminal-coated resin film for a secondary battery is mentioned above, the difference between the melt flow rate of the core layer and the surface layer is in the range of 5 g / 10 minutes or more and 30 g / 10 minutes or less, so the role of the core layer and the surface layer can be clearly distinguished. On the other hand, it is possible to ensure the insulation of the core layer and the coating of the resin on the surface layer.

The above-mentioned metal terminal-coated resin for a secondary battery In the film, in the case where the resin film is composed of three layers, and the intermediate layer of the resin film is a core layer, and the other layers are surface layers, the film thickness of the core layer may be in a range of 20 μm to 200 μm.

As long as the above-mentioned metal film for a secondary battery is coated with a resin film, the thickness of the core layer is 20 μm or more, so that insulation can be ensured even when heat-sealed or the like is applied during welding. In addition, since the thickness of the core layer is 200 μm or less, it is easy to control the film thickness, and the amount of resin is not increased, which can prevent excessive cost.

In addition, another aspect of the present invention is a battery pack. It is characterized by including the resin film coated with the metal terminal for secondary batteries of the said structure.

As long as it is the above battery pack, since the metal terminal for the secondary battery covered with the resin film is provided, it is possible to produce a battery pack having excellent insulation and adhesion.

In addition, another aspect of the present invention is a secondary battery. The manufacturing method of covering a resin film with a metal terminal is characterized by manufacturing a metal terminal-coated resin film for a secondary battery having the above-mentioned structure by blow molding.

As long as it is the said manufacturing method, even if it is a resin with a low melt flow rate, the extrusion-molding blow molding method can be used, and the metal terminal-coated resin film for secondary batteries can be stably produced.

According to one aspect of the present invention, it is possible to provide a metal terminal-coated resin film for a secondary battery, which can ensure the filling properties, adhesiveness, insulation properties, shape retention properties of the sealant, and excellent overall performance of the end portion of the lead, and Provided are a method for manufacturing the metal terminal-coated resin film for a secondary battery, and a battery pack using the metal terminal-coated resin film for a secondary battery.

10‧‧‧Laminated packaging materials for secondary batteries

11‧‧‧Inner resin layer

12‧‧‧Inner layer side adhesive layer

13‧‧‧Anti-corrosive treatment layer

14‧‧‧ barrier layer

15‧‧‧ Outer side adhesive layer

16‧‧‧ Outer

20‧‧‧ Splice

21‧‧‧ surface

22‧‧‧ Nuclear layer

23‧‧‧ Surface

24‧‧‧ Sealant

25‧‧‧Corrosion-resistant protective layer

26‧‧‧Guide metal layer

27‧‧‧ Guide

27a‧‧‧ Guide end

27b‧‧‧Guide corner

The end of X‧‧‧ guide

Corner of Y‧‧‧ Guide

Z‧‧‧ only consists of sealant

FIG. 1 is a cross-sectional view schematically showing the configuration of a laminated packaging material for a lithium ion battery.

Fig. 2 is a cross-sectional view schematically showing the structure of a three-layer tab sealant.

Fig. 3 (a) is a cross-sectional view schematically showing a general structure of a tab, and (b) is a cross-sectional view schematically showing a detailed structure of a tab.

Hereinafter, the tabs according to the embodiments of the present invention will be described in detail. 20. 3 (a) and (b) are cross-sectional views showing an example of the tab 20. As shown in FIGS. 3 (a) and (b), in the connecting piece 20, the three-layer sealant 24 and the guide metal layer 26 are adhered through the corrosion-resistant protective layer 25. Here, a member including the guide metal layer 26 and the corrosion-resistant protective layer 25 is referred to as a guide 27. The sealant 24 has the following structure in order from the guide 27 to the outside: the sealant surface layer (hereinafter simply referred to as the "surface layer") 21, the sealant core layer (hereinafter simply referred to as the "core layer") 22, and the sealant surface layer ( Hereinafter referred to as "surface layer") 23.

<Seal layer 21, 23>

The surface layers 21 and 23 must be resins having excellent adhesion to the guide sheet 27 and the polyolefin resin. The surface layers 21 and 23 are preferably acid-modified polyolefin resins obtained by graft-modifying maleic anhydride onto a polyolefin resin. The surface layer 21 in contact with the inner resin layer 11 (refer to FIG. 1) of the packaging material 10 and the surface layer 23 in contact with the guide 27 may use different resins, but if different resins are used for the seals The front and back surfaces of the glue 24 have different physical properties from the front and back surfaces of the sealant 24, which may result in reduced productivity. Therefore, it is preferable to use the same resin for the surface layer 21 and the surface layer 23.

In addition, because the melt flow rate of the core layer 22 is 0.1 g / 10 In the range of more than 2.5 g / 10 minutes, and the difference between the melt flow rate of the core layer 22 and the surface layers 21 and 23 is in the range of 5 g / 10 minutes and 30 g / 10 minutes, the melt flow of the surface layers 21 and 23 The ratio is more preferably within a range of 5.1 g / 10 minutes to 32.5 g / 10 minutes. The melt flow rates of the surface layers 21 and 23 are not limited to a single value because the difference between the core layer 22 and the core layer 22 is important. However, considering the filling properties for the end portion 27a of the guide, it is more suitable to be 7g / 10. Within the range of more than 20g / 10 minutes. If the melt flow rates of the surface layers 21 and 23 are less than 5.1 g / 10 minutes, the filling of the end portion 27a of the guide sheet during melting is insufficient. In addition, when the melt flow rates of the surface layers 21 and 23 exceed 32.5 g / 10 minutes, the viscosity during film formation is too low, which may cause generation of holes and the like.

The melt flow rate of the core layer 22 and the surface layers 21 and 23 When the difference exceeds 30 g / 10 minutes, the melt flow rates of the surface layers 21 and 23 become too large, and the resin fluidity becomes too high during welding, resulting in unstable welding. In addition, if the difference in the melt flow rate between the core layer 22 and the surface layers 21 and 23 is less than 5 g / 10 minutes, the difference in the melt flow rate is too small, and the respective performances of the core layer 22 and the surface layers 21 and 23 cannot be exhibited.

The film thickness of the surface layers 21 and 23 should be more than 10 μm and less than 300 μm Within range. If the film thicknesses of the surface layers 21 and 23 are less than 10 μm, the amount of resin flowing in to fill the guide end portion 27 a cannot be ensured, resulting in insufficient filling. In addition, when the film thickness of the surface layers 21 and 23 exceeds 300 μm, it is difficult to control the film thickness at the time of extrusion such as blow molding, and an increase in the amount of resin becomes a cause of increasing costs.

The melting points of the surface layers 21 and 23 are preferably 100 ° C or higher and 170 ° C or lower. Within the following range. Regarding the melting point, it is necessary to consider both the core layer 22 and the inner layer resin layer 11 of the packaging material 10, so it is difficult to limit the melting point only to the surface layers 21 and 23. For example, when the core layer 22 and the inner layer resin layer 11 are formed of a polyethylene-based resin, it is desirable that the same polyethylene-based resin is used for the surface layers 21 and 23 and the melting point is around 100 ° C. When the core layer 22 and the inner layer resin layer 11 are formed of a polypropylene-based resin, a resin having a melting point in the range of 130 ° C. to 170 ° C. is suitable.

<Sealing core layer 22>

In consideration of the adhesion with the surface layers 21 and 23, the core layer 22 is preferably a polyolefin resin. The melt flow rate of the core layer 22 is preferably within a range from 0.1 g / 10 minutes to 2.5 g / 10 minutes. If the melt flow rate of the core layer 22 is less than 0.1 g / 10 minutes, the melt viscosity will be too low, making it difficult to form a film. On the other hand, in a case where the melt flow rate of the core layer 22 exceeds 2.5 g / 10 minutes, and in a case where welding is performed at the time of making a tab, it is difficult to ensure the above-mentioned insulation and it is difficult to perform heat sealing with the packaging material 10 Maintain shape. From the viewpoint of productivity and the aforementioned performance, the melt flow rate of the core layer 22 is more preferably within a range of 0.5 g / 10 minutes or more and 1.5 g / 10 minutes or less.

The thickness of the core layer 22 is preferably within a range of 20 μm to 200 μm. When the film thickness of the core layer 22 is less than 20 μm, the film thickness is thin, and it is difficult to maintain the shape during the above-mentioned welding and heat sealing. In addition, during the above-mentioned welding and heat sealing, the surface layers 21 and 23 may have a large melt flow rate and a large amount of resin may flow, which may reduce the film thickness of the corner portion 27b of the guide. In the corner 27b of the guide, the film thickness of the surface layers 21 and 23 may be Since it becomes extremely small, it is necessary to secure the film thickness in the corner portion 27b of the guide with the core layer 22. When the film thickness of the core layer 22 is less than 20 μm, the total thickness of the corner portion 27 b of the guide piece is reduced, and the insulation properties are reduced. In addition, when the film thickness of the core layer 22 exceeds 200 μm, as in the case of the surface layers 21 and 23, it is not only difficult to control the film thickness during extrusion such as blow molding, but an increase in the amount of resin has also become a major cause of cost increase.

The melting point of the core layer 22 is preferably within the range of 100 ° C. to 170 ° C. for the same reason as the surface layers 21 and 23. In order to ensure the film thickness of the core layer 22 more reliably, it is also useful to set the melting point of the core layer 22 to be higher than that of the surface layers 21 and 23.

<Guide 27>

The material of the guide piece 27 is related to the material of the current collector in the secondary battery. For example, in a lithium ion battery, since aluminum is used as the current collector of the positive electrode, it is also preferable to use aluminum as the positive electrode terminal for the guide 27. More specifically, considering the corrosion resistance of the electrolytic solution, the guide piece 27 is made of an aluminum material having a purity of 97% or higher, such as 1N30, and the heat-sealed portion of the tab 20 and the packaging material 10 is also bent. For the purpose of additional flexibility, it is desirable to use a metal material whose texture is adjusted by Annealing. In addition, in the lithium ion battery, although copper is used as the current collector of the negative electrode, untreated copper is rarely used in the corrosion-resistant surface of the negative electrode terminal, and nickel-plated copper or nickel is preferably used.

The film thickness of the guide piece 27 is determined according to the size and capacity of the battery. The size of the guide piece 27 is 50 μm or more, and about 100 μm to 500 μm may be used for vehicle batteries and accumulators. Since it is required to reduce the resistance of the guide sheet 27, the film thickness of the guide sheet can be further increased. When the thickness of the guide is increased, the thickness of the sealant should also be increased. In the sealant 24, since the ends of these large guides must be filled, as in this embodiment, it is important to perform functional separation on the surface layers 21, 23 and the core layer 22, and it is important to set the optimal film thickness and melt flow rate. . In addition, it is effective to perform an anticorrosive treatment on the guide piece 27. In a secondary battery such as a lithium ion battery, since the electrolytic solution contains a corrosive component such as LiPF ₆ (lithium hexafluoride phosphate), the guide piece 27 must be subjected to an anticorrosive treatment.

<Manufacturing Method of Sealant 24>

As a method for manufacturing the sealant 24, three-layer blow molding is suitable. As a general extrusion molding method, there are a T-die method, a blow molding method, and the like, but in the T-die method, it is difficult to extrude a resin having a small melt flow rate. On the other hand, in a case where the melt flow rate is large, the blow molding method is difficult to maintain a bubble film, and voids or cracks may be generated in the film. In contrast, in the case of extruding a resin having a small melt flow rate, the shape of the bubble film is stable, and a film with less uneven film thickness can be formed.

Therefore, as in this embodiment, in the case of extruding a film containing a resin having a low melt flow rate, the blow molding method is most suitable. In the case where the surface layer 21 and the surface layer 23 are the same material, two types of three-layer extrusion molding are formed.

The extrusion temperature should preferably be in a temperature range of 180 ° C to 300 ° C, and more preferably in a range of 200 ° C to 250 ° C. If the extrusion temperature is less than 180 ° C, the resin will not be sufficiently melted and the melt viscosity will be too high, which may cause the extrusion from the screw to become unstable. On the other hand, when the extrusion temperature exceeds 300 ° C., the oxidation and deterioration of the resin become intense, and the quality of the film is reduced.

The rotation speed of the screw, the blow ratio, and the extrusion speed (Haul-Off Speed) should be appropriately selected relative to the set film thickness. In addition, the film thickness ratio of the three layers can be adjusted by changing the rotation speed of the screw.

<Fusion method>

Adhesion of the sealant 24 and the guide sheet 27 manufactured by the above-mentioned manufacturing method is performed by simultaneously performing "melting the core layer 22 by heating" and "adhering the sealant 24 and the guide sheet 27 by pressure" simultaneously. Thermal welding. In order to obtain sufficient peel strength, the heating temperature must be equal to or higher than the melting point of the resin of the core layer 22. In addition, when the melting point of the core layer 22 of the sealant 24 and the surface layers 21 and 23 are different, the heating temperature should be lower than the melting point of the core layer 22, and the heating temperature should be set if the core layer 22 is not provided. Below the melting point of the resin constituting the outer layer 16 of the packaging material 10. Specifically, the heating temperature is preferably about 140 ° C to 170 ° C. Heating and pressing time must also be determined in consideration of peel strength and productivity, and the pressing time should be about 1 second to 60 seconds. However, in the case where production takt time is a priority, heat welding can be performed in a short time at a temperature exceeding 170 ° C. In the above manufacturing method, conditions of about 170 ° C to 200 ° C and about 3 seconds to 20 seconds can also be applied.

<Packing material 10>

In general, the packaging material 10 is formed in the following order from the inner layer: the inner layer resin layer 11, the inner layer side adhesive layer 12, the anti-corrosion treatment layer 13, the barrier layer 14, the anti-corrosion treatment layer 13, and the outer layer side Next, the agent layer 15 and the outer layer 16.

As a component which comprises the inner-layer resin layer 11, a polyolefin resin, or the acid which graft-modified maleic anhydride etc. to the polyolefin resin is mentioned, for example. Modified polyolefin resin. Examples of the polyolefin resin include low-, medium-, and high-density polyethylene; ethylene-α-olefin copolymers; homo-, block-, or random polypropylenes; propylene-α-olefin copolymers, and the like. These polyolefin resins may be used singly or in combination of two or more kinds.

In addition, the inner resin layer 11 may be a single-layer film or a layer. A multilayer film having a plurality of layers. In accordance with necessary functions, for example, from the viewpoint of imparting moisture resistance, a multilayer film in which a resin such as an ethylene-cyclic olefin copolymer or polymethylpentane is sandwiched may be used for the inner resin layer 11. Furthermore, the inner resin layer 11 may be blended with various additives, such as a flame retardant, a slip aid, an anti-blocking agent, an antioxidant, a light stabilizer, a tackifier, and the like. The thickness of the inner resin layer 11 is preferably in a range of 10 μm to 150 μm, and more preferably in a range of 30 μm to 80 μm. In the case where the thickness of the inner resin layer 11 is less than 10 μm, the heat-sealing adhesiveness of the packaging materials 10 and the adhesiveness with the tab sealant 24 may be lowered. When the thickness exceeds 150 μm, the cost increases The main reason.

As the inner-layer-side adhesive layer 12, a well-known material such as a general dry laminating adhesive or an acid-modified hot-melt resin can be used.

Although it is preferable to form the anti-corrosion treatment layer 13 on both the surface and the back surface of the barrier layer 14 from a performance point of view, based on cost considerations, it may be formed on only one side.

As the barrier layer 14, for example, aluminum, stainless steel, or the like can be used. From the viewpoint of cost and weight (density), aluminum is suitable.

As the outer-layer-side adhesive layer 15, for example, a general polyurethane-based adhesive such as a polyester polyol, a polyether polyol, or a propylene glycol-based polyol can be used.

As the outer layer 16, a single film or a multilayer film such as nylon or PET can be used. As with the inner resin layer 11, various additives such as a flame retardant, a slip aid, an anti-caking agent, an oxidation inhibitor, a light stabilizer, a tackifier, and the like can be blended in the outer layer 16. In addition, an electrolyte-insoluble resin may be laminated, or the electrolyte-insoluble resin component may be applied as a countermeasure against liquid leakage.

<Heat-sealing method of packaging material 10>

When manufacturing the battery pack, the packaging material 10 and the tabs (which are formed by welding the tab guides 27 and the tab sealant 24) 20 are heat-sealed. Compared with the heat sealing of only the packaging material portion, since the heat sealing system of the tab portion is sandwiched by the tab 20, more heat is required. The temperature condition for heat sealing is preferably in a temperature range of 160 ° C to 210 ° C. If it is lower than 160 ° C, poor adhesion is likely to occur due to insufficient melting of the tab sealant 24, and when it exceeds 210 ° C, the nylon generally used for the outer layer 16 of the packaging material 10 may melt. The heat-sealing time is preferably within a time range of 1 second to 10 seconds. If the heat-sealing time is less than 1 second, poor adhesion is likely to occur due to insufficient melting, and if it exceeds 10 seconds, the production cycle will be longer and the productivity will be lowered.

In addition, since the tab portion is thicker than the other portions, there are cases in which, for example, a counter bore is used for a heat seal bar used in heat sealing, and only in the tab portion and its vicinity. The packaging material 10 applies the most suitable pressure to the heat-sealed portion.

[Example]

Although examples of the present invention are shown below, the present invention is not limited thereto. Common conditions of the examples and comparative examples are as follows.

(1) Production of splice 20

As the guide 27, a width of 5 mm, a length of 30 mm, and a thickness of 100 μm was used. The material of the positive electrode is aluminum, and the material of the negative electrode is nickel. Both the positive and negative electrodes are subjected to non-chrome surface treatment.

The composition, film thickness, and the like of the sealant 24 are shown in detail in each of the examples, and those having a size of 15 mm in width and 10 mm in length are used. The sealant 24, the guide 27, and the sealant 24 are sequentially laminated, and the welding is performed under the conditions of a welding temperature of 150 ° C and a welding time of 10 seconds.

(2) Production of battery pack

As the packaging material 10, nylon (25 μm in thickness), polyester polyol adhesive (5 μm in thickness), aluminum foil (40 μm in thickness, A8079-O material), and acid-modified polypropylene (hereinafter also referred to as “ "PPa", a thickness of 30 µm), polypropylene (hereinafter also referred to as "PP", a thickness of 40 µm). Both sides of the aluminum foil are subjected to a non-chrome-based surface treatment. The size of the packaging material 10 is 50 mm × 90 mm, the long side is folded into two equal portions, and the positive electrode and the negative electrode are heat-sealed together on the side of the side having a width of 45 mm. Heat sealing was performed at 190 ° C for 5 seconds. The remaining two sides without the tabs were heat-sealed at 190 ° C for 3 seconds. First, heat-seal the side opposite to the folded side, and then add 2 ml of IiPF ₆ (lithium hexafluoride) electrolyte to the mixed solution of diethyl carbonate and ethyl carbonate. The opposite sides of the tab 20 are heat-sealed. In this way, a battery pack for evaluation of the tabs 20 was produced without battery elements such as a current collector.

[Example 1]

The surface layer A and the surface layer B are made of the same material, and the sealant is produced by two three-layer blow molding methods (hereinafter also referred to as "blow molding methods"). Here, the surface layers A and B correspond to the surface layers 21 and 23 of the above embodiment. As the surface layers A and B, acid-modified polypropylene (PPa) having a melt flow rate of 15 g / 10 minutes and a melting point of 140 ° C was used, and the core layer was polypropylene (PP) having a melt flow rate of 1.0 g / 10 minutes and a melting point of 160 ° C. Film formation was performed such that the melting temperature was 210 ° C., the foaming ratio was 2.2, and the total film thickness was 150 μm (the surface layer A / core layer / surface layer B film thickness was 45/60/45 μm).

[Example 2]

For the surface layers A and B, PPa with a melt flow rate of 10 g / 10 minutes and a melting point of 140 ° C was used. For the core layer, PP with a melt flow rate of 0.7 g / 10 minutes and a melting point of 155 ° C was used. Making.

[Example 3]

A sealant was produced in the same manner as in Example 1 except that the total film thickness of the sealant was 100 μm (the film thickness of the surface layer A / core layer / surface layer B was 30/40/30 μm).

[Example 4]

A sealant was produced in the same manner as in Example 2 except that the total film thickness of the sealant was 100 μm (the film thickness of the surface layer A / core layer / surface layer B was 30/40/30 μm).

[Comparative Example 1]

A sealant was produced in the same manner as in Example 4 except that a PP having a melt flow rate of 7 g / 10 minutes and a melting point of 160 ° C was used for the core layer.

[Comparative Example 2]

A sealant was produced in the same manner as in Example 1 except that the surface layers A and B used PPa having a melt flow rate of 2 g / 10 minutes and a melting point of 135 ° C.

[Comparative Example 3]

A sealant was produced in the same manner as in Example 1 except that the total film thickness of the sealant was 50 μm (the film thickness of the surface layer A / core layer / surface layer B was 15/20/15 μm).

[Comparative Example 4]

A sealant was produced in the same manner as in Example 2 except that the total film thickness of the sealant was 50 μm (the film thickness of the surface layer A / core layer / surface layer B was 15/20/15 μm).

[Comparative Example 5]

A sealant was produced in the same manner as in Example 1 except that the surface layers A and B used PP having a melt flow rate of 15 g / 10 minutes and a melting point of 140 ° C.

[Comparative Example 6]

A sealant was produced in the same manner as in Example 2 except that the surface layers A and B used PP having a melt flow rate of 10 g / 10 minutes and a melting point of 140 ° C.

[Comparative Example 7]

A sealant was produced in the same manner as in Example 1 except that the method of forming the sealant film was changed to a T-die method with a melting temperature of 230 ° C.

[Comparative Example 8]

A sealant was produced in the same manner as in Example 2 except that the film-forming method of the sealant was changed to a T-die method with a melting temperature of 230 ° C.

<Evaluation of Sealant>

The produced tab and battery pack were evaluated by the following methods.

<Evaluation 1: Film-forming property>

When molding the sealant, the finished film is not good if it has no wrinkles or holes.

<Evaluation 2: Shape stability>

Measure the dimensional change of the sealant part made by the above method, and it is a good product with a design value within ± 300 μm.

<Evaluation 3: Filling property of end of guide piece>

The piecing sheet made by the above method is dyed with a highly permeable dyeing solution (manufactured by Dafeng Engineering Materials Co., Ltd., MICRO CHECK). The liquid permeates the end of the guide and the colored part is a defective product; the corner of the guide The filling is sufficient, and the liquid does not penetrate the end of the guide is good.

<Evaluation 4: Adhesiveness>

The adhesion strength between the contact piece and the guide piece produced by the above method was measured. The measurement was performed using a tensile tester (manufactured by Shimadzu Corporation) under conditions of a peeling angle of 180 degrees and a peeling speed of 30 mm / min. Both the positive and negative electrodes have good peel strengths above 2.5N / 5mm.

<Evaluation 5: Insulation property>

The tester was used to measure the insulation between the negative electrode lead of the battery pack for evaluation produced in the above-mentioned manner and the packaging material. In 100 tests, the short circuit is less than 10 times as good.

<Evaluation Results>

Table 1 shows the evaluation results. In Table 1, "○" indicates a good product, "×" indicates a defective product, and "-" indicates that it cannot be measured.

In Examples 1 to 4, all of the items of film forming property, shape stability, end piece filling property, adhesiveness, and insulation properties are suitable, and excellent shape stability can be stably produced, and the end piece filling is also stable. Adequate sealant with excellent adhesion and insulation.

On the other hand, in Comparative Example 1, since the melt flow rate of the core layer was too large, the shape stability and insulation properties were lowered.

In Comparative Example 2, since the melt flow rates of the surface layers A and B were too small, the filling properties of the end portions of the guide sheet were insufficient.

In Comparative Examples 3 and 4, since the film thickness of the core layer was too thin, the insulation properties were insufficient.

In Comparative Examples 5 and 6, since the surface layers A and B used PP, the adhesion was insufficient.

In Comparative Examples 7 and 8, since the film was formed by a T-die method instead of the blow molding method, wrinkles occurred in the film, and a good film could not be produced.

Based on the above results, as long as it is a resin film coated with a metal terminal for a secondary battery according to this embodiment, it is possible to provide an excellent overall performance that can ensure the filling properties, adhesiveness, insulation, and seal shape maintenance of the end portion of the lead. The metal terminal for a secondary battery is covered with a resin film.

Claims (9)

A metal terminal-coated resin film for a secondary battery is a laminated metal terminal-coated resin film for a secondary battery that covers a metal terminal connected to a positive or negative electrode of a secondary battery. The resin film is characterized in that: When the resin film has a three-layer structure and the intermediate layer is a core layer and the other layers are surface layers, the melt flow rate of the core layer is within a range of 0.1 g / 10 minutes to 2.5 g / 10 minutes, and The difference between the melt flow rate of the core layer and the surface layer is in a range of 5 g / 10 minutes or more and 30 g / 10 minutes or less, and the film thickness of the core layer is in a range of 20 μm or more and 200 μm or less. The surface layer on the contact side is formed of an acid-modified polyolefin resin, and the core layer is formed of a polyolefin resin. The resin film for a metal terminal for a secondary battery according to claim 1, wherein the surface layer opposite to the side in contact with the metal terminal is formed of an acid-modified polyolefin resin. The metal terminal-coated resin film for a secondary battery according to claim 1, wherein the acid-modified polyolefin resin is acid-modified polypropylene, and the polyolefin resin is polypropylene. The metal terminal-coated resin film for a secondary battery according to claim 2, wherein the acid-modified polyolefin resin is acid-modified polypropylene, and the polyolefin resin is polypropylene. The metal battery-coated resin film for a secondary battery according to any one of claims 1 to 4, wherein the melt flow rate of the surface layer is within a range of 7 g / 10 minutes or more and 20 g / 10 minutes or less. The secondary battery-coated metal film for a secondary battery according to any one of claims 1 to 4, wherein the melting point of each of the core layer and the surface layer is within a range of 100 ° C to 170 ° C, and the melting point of the core layer is set. Higher than the melting point of the surface layer. For example, the metal battery for a secondary battery of claim 5 is coated with a resin film, wherein the melting points of the core layer and the surface layer are within a range of 100 ° C to 170 ° C, and the melting point of the core layer is higher than the melting point of the surface layer . A battery pack comprising the metal terminal-coated resin film for a secondary battery according to any one of claims 1 to 7. A method for manufacturing a metal terminal-coated resin film for a secondary battery, which is characterized in that a metal terminal-coated resin film for a secondary battery according to any one of claims 1 to 7 is manufactured by blow molding.